As the father of an adult daughter and son, plus the grandfather of four knucklehead boys, I’ve learned some things about love.

All the hours logged as Dad and Poppy have often caused me to contemplate how different are the roles of mother and father, especially in the overt demonstration of parental love. It’s fascinating how the manifestation of this love differs between mother and father – biologically, emotionally and experientially.

A mother’s love, at once sweet and fierce, is observed in almost all animals, not just humans. No doubt you’ve heard this metaphor: “… as sweet as a mother’s love,” and this warning: “Don’t get between a momma bear and her cub.”

I have been the recipient of this kind of love and have witnessed it, and there truly is no other force in nature like it. But it has troubled me that there are no corresponding references for a father’s love. Could this be why Father’s Day is not quite as big a deal as Mother’s Day? I’m just saying …

A human father’s love is more often associated with words that are unfortunate, like “tough” and “discipline.” As a teenager, my own father once apologized to me when he thought his demonstration of love might seem “hard-boiled.”

Mothers occupy the pinnacle of parental love – with justification. And not to take anything away from them, but since a mother’s sweet love is as primal as the miracle of birth, they don’t have to work too hard to deliver it. But there’s a uniqueness about a father’s love that deserves a better rap. Here are two reasons:

Unlike a mother’s sweet love, a father’s tough love does not exist outside of homo sapiens.

When a father’s parental toughness is required, especially when applied to an indignant recipient (read: teenager), it requires a love that has found the courage to endure a negative response and a willingness to defer gratification – sometimes for years.

No one is more keenly aware of the distinction between these two demonstrations of love than a single parent, where both kinds are required of the same person, perhaps within minutes.

Mothers, please forgive any paternal bias you may detect, but here is my conclusion about parental love: The only force in the universe that comes close to a mother’s sweet love is a father’s tough love. But the latter is the harder job, and the return on investment almost always takes longer.